1. Field of the Invention
The present invention generally relates to an image sensor, and more particularly to a readout system and method with enhanced dynamic range for the image sensor.
2. Description of Related Art
Semiconductor based image sensors, such as charge-coupled devices (CCDs) or complementary metal-oxide-semiconductor (CMOS) sensors, are widely used, for example, in cameras or camcorders, to convert images of visible light into electronic signals that can then be stored, transmitted or displayed.
With respect to the readout system for an image sensor, the dynamic range is usually limited by the linear scale of an analog-to-digital converter (ADC). One conventional method for enhancing the dynamic range involves increasing the resolution of the ADC. This method, however, tends to increase both the cost and latency. Another conventional method for enhancing the dynamic range seeks to combine long exposure-time image data (for a darker signal) with short exposure-time image data (for a brighter signal). Nevertheless, this method can be complex and time-consuming.
For the reason that conventional readout systems for an image sensor cannot effectively and economically enhance dynamic range, a need has arisen to propose a novel readout system for an image sensor that is capable of acting quickly and is non-complex.